Canthigaster valentini is a reef-associated species found among coral heads and rocks of sub-tidal lagoons and seaward reefs (Smith and Heemstra 1986, Cornic 1987, Tyler 1967) at depths of 1 to 55 m. It is also found in seagrass beds, and has been known to settle on and associate with artificial reefs (Leis et al. 2002). This species forages on the benthos, feeding mainly on filamentous green and red algae, tunicates, and on smaller amounts of corals (Cole et al. 2008), bryozoans, polychaetes, echinoderms, molluscs, and brown and coralline red algae. By preying on corals, C. valentini may negatively impact their post-bleaching recovery (McClanahan et al. 2005)

Canthigaster valentini forms shoals of 10–100 individuals or more, often with the filefish, Paraluteres prionurus (about 5% of shoal), which mimics the toxic C. valentini to protect it from predators (Smith and Heemstra 1986, Cornic 1987). This species is also mimicked by juvenile coral trout, Plectropomus laevis (Frisch 2006). Maximum total length for this species is 11.0 cm or 110 mm male/unsexed (Smith and Heemstra 1986).

Canthigaster valentini is gonochoristic and sexes can be distinguished externally (Gladstone and Westoby 1988). It maintains a sex ratio very close to 1:1, and lives in social groups consisting of a single, sexually mature male, several mature females, and varying numbers of immature individuals (Gladstone 1987). Males are territorial and are often seen fighting (Kuiter and Tonozuka 2001). Spawning occurs at all times of the year. This species is territorial and haremic; males spawn with a different female each day (Lieske and Myers 1994). All sexually mature females are territorial females (Gladstone 1987). The territories of mature females were always enclosed within the territory of a single, mature male. (Gladstone 1987). Social and mating systems of this species are based upon female territoriality where polygyny results from males defending females occupying a certain territory (female-defense polygyny) (Gladstone 1987). Neither parent guards the eggs which are laid in a nest located in the female's territory (Gladstone 1987).

The eggs and larvae of this species are unpalatable to other species (Gladstone 1987). Larvae may have high survivorship as a result (Gladstone and Westoby 1988). The eggs of this species are spherical and strongly adhesive, 0.68–0.72 mm in diameter, possess a dense cluster of small oil droplets, and hatch around sunset three to five ays after fertilization (Stroud et al. 1989). Larvae of C. valentini colonize reefs at 13 mm total length and recruit at 45 mm total length (Lecchini and Galzin 2005).

Canthigaster spp. are known for their general lack of characters, and are generally differentiated on the basis of colour differences.

Tetraodontids are characterized by a tough skin that is often covered with small spinulous scales, a beak-like dental plate divided by a median suture, a slit-like gill opening anterior to the base of the pectoral fin, no pelvic fins, no fin spines, a single usually short-based dorsal fin, a single usually short-based anal fin, and no ribs. They are capable of inflating their abdomens with water when frightened or disturbed and are capable of producing and accumulating toxins such as tetrodotoxin and saxitoxin in the skin, gonads, and liver. The degree of toxicity varies by species, and also according to geographic area and season (Allen and Randall 1977, Allen and Erdmann 2012). Fishes in the family Tetraodontidae have the smallest vertebrate genomes known to date (Neafsey and Palumbi 2003).

There have been observed declines in the abundance of C. valentini in parts of its range (K. Carpenter pers. comm. 2011). Due to its affinity with coral reefs and seagrass beds, we infer that this is due to habitat loss in parts of its range.

As of 2008, fifteen percent of the world’s coral reefs were considered under imminent threat of being “Effectively Lost” (with 90% of the corals lost and unlikely to recover soon), with regions in East Africa, South and South-east Asia, and the wider Caribbean being the most highly threatened (Wilkinson et al. 2008). Of 704 zooxanthellate reef-building coral species which were assessed by using the IUCN Red List Criteria, 32.8% are in categories with elevated risk of extinction (Carpenter et al. 2008).

One-third of global seagrass species are currently experiencing population declines, and 21% of IUCN Red List assessed seagrass species are in threatened or Near Threatened categories primarily due to coastal development and pollution (Short et al. 2011).